Transcultural Validation of the French Version of the Functional Pain Scale "Defense and Veterans Pain Rating Scale"

The primary objective of this study is to validate the French translation of the multidimensional "Defence and Veterans Pain Rating Scale" (= functional pain scale).

The hypothesis is that the functional pain scale is a valid measurement instrument for acute and chronic pain evaluation in a wide range of patient groups: postoperative patients, hospitalized patients with non-surgical pain (medical, oncological, rehabilitative, geriatric, palliative), and ambulatory chronic pain patients.

The primary endpoint is construct validity assessed as the association (intraclass correlation coefficient) between the pain intensity noted on the functional pain scale and on the classical NRS pain scale.

In addition to the association with the NRS, construct validity will be assessed by correlation of pain intensity noted on the functional pain scale intensity with the pain intensity score of the BPI for chronic pain patients, and the item "severe pain time" of the International Pain Outcomes Questionnaire (8) for postoperative patients.

Content validity will be assessed in a subgroup of patient by the association of the values for pain intensity (0-10) on the functional pain scale and the corresponding word descriptors. A factor analysis of all items of the functional pain scale will be performed.

Internal consistency of the functional pain scale will be tested by calculating Cronbach's alpha across all items.

Criterion validity will be assessed in patients for whom mobilisation is an important therapeutic goal as the discrimation between patients who can be mobilized and those who can't because of pain, and patients who consider their pain as tolerable and those who do not.

This discrimative ability will also be compared to the classical numeric rating scale, as it is a potential advantage of the functional pain scale. For the numeric rating scale, a large overlap in pain intensity for patients who consider their pain as tolerable and those who do not has been found(9).

Sensitivity to change will be evaluated by comparing values before and after an analgesic treatment for a subgroup of patients with an initial pain intensity of at least 4/10 on the functional pain scale. However, since patients with high pain levels will not be able to fill in the questionnaire, this is only an exploratory endpoint of this study.

Patient and caregiver evaluation of ease of use will also be evaluated, as well as patient judgement of tolerable pain levels.

Inclusion criteria

• Patients with acute or chronic pain, either having undergone painful surgical procedures, or having a chronic pain consultation, or being hospitalized in oncology, rehabilitative, geriatric or palliative care with painful conditions
• French-speaking and able to understand the study information
• ≥18 years of age

Exclusion criteria

• Inability to understand the consent form and the questionnaire, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• Enrolment of the investigator, his/her family members, employees and other dependent persons